Phenylalanine is an amino acid, which means that it is one of the building blocks for proteins. Your body cannot synthesize it, so it makes up an essential part of your diet. However, phenylalanine can cause negative health effects in some initials -- people suffering from phenylketonuria, or PKU, can consume only limited amounts of this amino acid, because they do not metabolize it properly. Many different foods contain this amino acid, and pose a health risk to people with PKU.
Foods that are derived from animals are typically rich in protein. Because phenylalanine is an amino acid, foods that are high in protein often contain significant amounts of phenylalanine. As a result, pork, poultry, chicken, beef, eggs, yogurt, cheese and milk commonly are good sources of phenylalanine, the University of Maryland Medical Center reports.
Nuts and legumes, such as peanuts, are also high in protein. Consequently, foods such as walnuts, peanuts, peanut butter, hazel nuts and Brazil nuts contain relatively high quantities of phenylalanine. The protein found in soy also contains phenylalanine. Phenylalanine can be found in soybean flour, soy flour isolate and tofu. Other legumes -- including black beans, kidney beans and chickpeas -- are all high in protein and boost your phenylalanine intake.
Cacao is the bean that is used to make chocolate and cocoa. Cocoa powder and the chocolate that is used for making hot chocolate or chocolate-flavored drinks have moderate phenylalanine, according to FoodFacts. Cocoa powder contains more than seven times as much phenylalanine per gram compared to drinking chocolate-flavored drinks.
Grains and other carbohydrates typically do not contain large quantities of protein and are often fairly low in phenylalanine. The exceptions to this rule are breads and other grain products that are made with reduced starch.
Phenylalanine can also be found in products that contain artificial sweeteners, such as aspartame. Despite the warning label that is present on all products that have aspartame, this sweetener is safe for use. This warning is only printed for the benefit of people who have phenylketonuria.
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